The present invention generally relates to metal interconnect structures, and particularly to self-forming diffusion barriers.
Metal interconnect structures are the primary means of connecting microelectronic devices. Such interconnect structures typically take the shape of wires, trenches, or vias formed in dielectric layers above the microelectronic devices and may typically be formed by depositing a dielectric layer, etching a trench in the dielectric layer and filling the trench with metal. To prevent electromigration of the metal within the trench and to prevent material from the metal and the dielectric from diffusing into each other, a liner may be deposited into the trench prior to filling the trench with metal. Typically, this liner consists of a layer of tantalum, tantalum nitride, or both; though other liner materials are known in the art.
However, as the dimensions of microelectronic devices continue to shrink, smaller interconnect structures are also required. As the interconnect structures shrink, the thickness of the liner becomes increasingly problematic, as it takes up a proportionally greater volume of the trench. Because the volume of metal in the trench is reduced, the resistance of the interconnect structure increases, subsequently decreasing overall device performance. Ultimately the interconnect structure may become so small that it is not possible to effectively deposit the liner in the trench, rendering the device inoperable. Therefore, a means of forming a diffusion barrier that maximizes the metal volume within the trench is desirable.